Benthos LPI Surveys

Overview

The Line Point Intercept (LPI) protocol is used to quantify benthic community composition at Pristine Seas UVS sites. Divers swim along a fixed transect line and record the benthic taxon or category directly beneath a series of regularly spaced sampling points.

Points are recorded every 20 cm along a 50-meter transect, yielding 250 point intercepts per station, typically divided into five 10-meter sections (50 points each). In some cases, shorter transects (e.g., 30 m) are used, resulting in fewer total points.

This method yields high-resolution estimates of percent cover for key benthic groups—such as hard coral, macroalgae, crustose coralline algae (CCA), and cyanobacteria—and supports assessments of reef condition and spatial variability.

LPI data are organized across three interlinked tables:

  • uvs.lpi_stations - Metadata and summary metrics for each LPI transect station
  • uvs.lpi_counts - Point intercept counts per morphotaxon, station, and section
  • uvs.lpi_cover_by_taxa - Percent cover summaries by taxon or functional group, per station

All records are linked via ps_station_id. Taxa are harmonized using accepted_name and accepted_aphia_id, which represent the minimum resolved taxonomic level per morphotaxon.


Tables


Stations (uvs.lpi_stations)

Each row in this table represents a single depth-stratified LPI survey at a UVS site. Fields include spatial and habitat metadata, survey effort (e.g., transect length, number of sections, total points), and benthic summary metrics such as percent cover of hard coral, CCA, and cyanobacteria.

Table 1: Schema for uvs.lpi_stations: metadata and summary metrics for each LPI transect station
Field Type Required Description
ps_station_id STRING true Unique station ID (ps_site_id_depth).
ps_site_id STRING true Foreign key to uvs.sites.
exp_id STRING true Expedition ID (ISO3_YEAR).
method STRING true Survey method (uvs).
protocol STRING true Survey protocol (benthic_lpi).
divers STRING true Divers who conducted the LPI transects.
region STRING true Region name.
subregion STRING true Subregion name.
locality STRING false Optional local feature (e.g., reef, bay).
latitude FLOAT true Latitude of station (decimal degrees, WGS84).
longitude FLOAT true Longitude of station (decimal degrees, WGS84).
date DATE true Date of LPI survey.
time TIME true Start time of the LPI transects (24-hour format).
depth_m FLOAT true Average station depth (m).
depth_strata STRING true Depth bin: supershallow, shallow, or deep.
habitat STRING true Habitat type (e.g., fore reef, patch reef).
exposure STRING true Exposure type (e.g., windward, leeward, lagoon).
transect_distance INTEGER true Total length of transect surveyed (m).
n_sections INTEGER true Number of 10m sections surveyed (typically 5).
n_points INTEGER true Total number of points sampled across all transects.
pct_coral FLOAT false Percent of points classified as hard coral (Scleractinia).
pct_cca FLOAT false Percent of points classified as crustose coralline algae (CCA).
pct_cyano FLOAT false Percent of points classified as cyanobacteria.
notes STRING false Optional QA or field notes.

Counts (uvs.lpi_counts)

This table stores summarized point intercept data from LPI transects. Each row represents the number of points at which a given morphotaxon was recorded within a specific station and transect section.

Each record includes:

  • A diver-entered morphotaxon label (e.g., “Porites sp.”, “CCA”, “Turf”)
  • A standardized accepted_name and accepted_aphia_id (minimum taxonomic resolution)
  • A functional group classification (e.g., coral, CCA, macroalgae)

The n_points field indicates how many times the morphotaxon was recorded in the section. This format supports fine-scale spatial summaries while preserving compatibility with aggregate-level analyses.

Table 2: Schema for uvs.lpi_counts: point intercept counts by morphotaxon and transect section
Field Type Required Description
ps_station_id STRING true Foreign key linking to uvs.lpi_stations.
diver STRING true Name of the diver who recorded the data.
station_label STRING true Field-assigned stratum label (e.g., shallow, deep).
depth_m FLOAT true Recorded depth (m) at which the LPI transect was conducted.
section INTEGER true Transect section number (typically 1–5 for 10 m intervals).
morphotaxon STRING true Field-entered morphotaxon label (e.g., ‘Porites sp.’, ‘CCA’, ‘Turf’).
accepted_name STRING true Standardized scientific name representing the minimum identifiable taxon.
accepted_aphia_id INTEGER true WoRMS AphiaID — foreign key to taxonomy.benthic.
functional_group STRING true Functional group classification (e.g., coral, CCA, turf, macroalgae).
n_points INTEGER true Number of point intercepts assigned to the morphotaxon in the given section.
notes STRING false Optional comments or QA annotations.

Cover by Taxa (uvs.lpi_cover_by_taxa)

This table contains station-level summaries of benthic percent cover by taxon or group. Each row represents a unique combination of ps_station_id and benthic taxon, with cover calculated as the proportion of total points assigned to that taxon.

Taxonomic identity is standardized via accepted_name and accepted_aphia_id. Functional group assignments support grouped summaries such as total coral, algae, or CCA cover, and are consistent with those used across reef condition assessments and visualizations.

Table 3: Schema for uvs.lpi_cover_by_taxa: percent cover by taxon at each LPI station
Field Type Required Description
ps_station_id STRING true Unique station ID (ps_site_id_depth), e.g., CHL_2024_uvs_001_20m.
accepted_name STRING true Scientific name of the benthic taxon (Genus species) or category.
accepted_aphia_id INTEGER true Unique AphiaID from WoRMS; foreign key to taxonomy.benthic.
functional_group STRING true Functional group classification (e.g., coral, CCA, turf, macroalgae).
depth_m FLOAT true Mean depth (m) of the station.
depth_strata STRING true Depth bin label: supershallow, shallow, or deep.
region STRING true Region name.
subregion STRING true Subregion (e.g., island, gulf, reef complex).
locality STRING false Optional local feature (e.g., reef, bay, cove).
habitat STRING true Dominant habitat type at the station.
exposure STRING true Wave/wind exposure at the station (windward, leeward, lagoon).
n_points INTEGER true Total number of point intercepts assigned to the taxon.
pct_cover FLOAT true Percent cover calculated as n_points divided by total points at the station * 100.